The present invention relates to flexible covers or tarping systems for open-topped containers and particularly concerns a mechanism for restraining the flexible cover or tarp on the container.
Many hauling vehicles, such as dump trucks, include open-topped containers used for hauling or storing various materials. In a typical dump truck application, the dump body is used to haul a variety of particulate material, such as gravel and the like, as well as organic materials, such as grain or produce.
Depending upon the nature of the materials stored in the open-topped container, it is often desirable to provide a cover for the container. A cover is particularly valuable when the containers are part of a vehicle, such as a dump truck. Rigid covers are well known that may be hinged from one end of the container body and pivoted from an open to a closed position. While rigid covers may be acceptable for stationary containers, the same is usually not true for land vehicles. In this industry, the rigid covers have given way to flexible cover systems. Systems of this type utilize a flexible tarpaulin that can be drawn from a stowed position at one end of the container, to a deployed position covering the open top of the vehicle container or bed. The flexible cover or tarpaulin is preferable in this arena because it can be easily stowed when the cover is not necessary, such as when a dump truck is being loaded or emptied. In addition, the flexible cover is generally easier to deploy than a rigid cover.
A variety of flexible cover or tarping systems have been developed that are geared toward particular hauling vehicle applications. One such tarping system is the Easy Cover® Tarping System manufactured and sold by Aero Industries, Inc. An example of one form of the Easy Cover® Tarping System is shown in FIG. 1. The system includes a tarp deployment mechanism in the form of a U-shaped bail member 22 that is connected at a pivot mount 25 to the base of the container body 13 on vehicle 10. The horizontal section of the U-shaped bail is attached to the tarp 16. The tarp 16 can be preferably stowed by winding onto a tarp roller 19 at the forward end of the vehicle.
The pivot mount 25 and the tarp roller 19 can be of a variety of configurations that permit manual or powered deployment. In one typical installation the pivot mount 25 includes a torsion spring pack that is biased to rotate the bail member 22 (clockwise in the figure) to pull the tarp 16 over the top of the container 13. The tarp roller 19 is biased to resist this rotation of the bail member. In some versions, a manual crank rotates the tarp roller 19 to allow the tarp 16 to unfurl under the torsion force of the spring pack. In other versions, a motor controls the rotation of the tarp roller. The manual crank or motor are rotated in the opposite direction to pull the bail member 22 toward the front of the container body 13 and to thereby stow the tarp 16 in its open position.
One problem that is persistently faced with tarping systems of the type shown in FIG. 1 is the effect of air flow or wind as the vehicle is traveling. This problem becomes especially acute at high speeds. The tarpaulin 16 is affected in a number of ways by the air flow across a traveling vehicle. The front end of the vehicle creates turbulent air flow that travels along the length of the container body 13. This turbulence, which can be manifested by air vortices along the top of the container body, has a tendency to lift the flexible cover away from the top of the body.
Another problem is simply road vibration and shock, which can cause the bail member 22 to bounce on the back of the container body 13 when deployed. The problem is especially noticeable for systems in which the pivot mount utilizes a biased torsion spring pack. When the tarp is fully deployed, as shown in FIG. 1, the spring force is much less than when the tarp is stowed. This lower spring torsional force is unable to prevent the bail member from bouncing due to road shock or vibration.
This action of the tarp and bail member due to wind and vibration effects can be very noisy. The most deleterious effect is on the flexible tarping system itself. The constant flapping and bouncing can gradually wear the tarp and the tarping system components down, which decreases the longevity of the tarping system. In addition, when the tarp 16 is dislodged from its deployed position, the contents of the container body 13 are at risk of expulsion.
In order to address this problem, various systems have been devised to hold the tarp down against the container body. In one common system, a web of cords is deployed over the tarp cover 13 along the length of the container body. The ends of the cords can be attached to mounts fixed to the side of the body. In other systems, the bail member includes a tie down that can be manually attached to mounts at the rear of the body.
Still other systems rely upon a complicated array of mechanical, electrical or hydraulic structures to apply a constant tension along the length of the tarp. However, in most cases, the tension along the length of the tarp does not alleviate the problem of bellowing of the side edges of the tarp or bouncing of the bail member. In one approach shown in FIG. 1, the bail member 22 is seated within brackets 27 mounted to the rear of the container 13.
The prior approaches either require manual intervention or require sophisticated powered components to lock the bail arm in the deployed condition. There remains a need for a tarping system with a locking mechanism that is automatically operated to both lock and unlock the tarp from its deployed position.